U.S. patent number 5,448,981 [Application Number 08/291,325] was granted by the patent office on 1995-09-12 for regulated flow canister purge system.
This patent grant is currently assigned to Siemens Automotive Limited. Invention is credited to John E. Cook, William C. Gillier.
United States Patent |
5,448,981 |
Cook , et al. |
September 12, 1995 |
Regulated flow canister purge system
Abstract
The evaporative emission control system for an internal
combustion engine purges the vapor collection canister to the
intake manifold through a purge regulator controlled by the engine
ECU. The purge regulator comprises a diaphragm valve and an
electronic vacuum regulator. The purge regulator functions to allow
a purge flow rate correlated with a control signal from the engine
ECU and manifold vacuum, to maintain the purge flow rate
substantially constant in response to certain changes in the
magnitude of manifold vacuum, and to re-adjust the purge flow rate
in correlation with changes in the control signal from the engine
ECU. The diaphragm valve comprises a tapered valve element that
progressively reduces the flow restriction as the valve element is
increasingly opened.
Inventors: |
Cook; John E. (Chatham,
CA), Gillier; William C. (Chatham, CA) |
Assignee: |
Siemens Automotive Limited
(Chatam, CA)
|
Family
ID: |
27504334 |
Appl.
No.: |
08/291,325 |
Filed: |
August 16, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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76220 |
Jun 14, 1993 |
|
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954517 |
Sep 30, 1992 |
5226398 |
|
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|
722765 |
Jun 27, 1991 |
5199404 |
|
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591219 |
Oct 4, 1990 |
5050568 |
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490791 |
Mar 8, 1990 |
5054455 |
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Current U.S.
Class: |
123/520;
123/516 |
Current CPC
Class: |
F02D
41/004 (20130101); F02M 25/0836 (20130101); F02B
61/045 (20130101) |
Current International
Class: |
F02D
41/00 (20060101); F02B 61/00 (20060101); F02B
61/04 (20060101); F02M 037/04 () |
Field of
Search: |
;123/520,519,516,518,521,198D |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller; Carl S.
Attorney, Agent or Firm: Boller; George L. Wells; Russel
C.
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is a file wrapper continuation of Ser.
No.08/076,220 file Jun. 14, 1993 which is a continuation of Ser.
No. 07/954,517 filed Sep. 30, 1992, now U.S. Pat. No. 5,226,398,
which is a continuation of Ser. No. 07/722,765 filed Jun. 27, 1991,
now U.S. Pat. No. 5,199,404, which is a continuation-in-part of
Ser. No. 07/591,219, filed Oct. 4, 1990, now U.S. Pat. No.
5,050,586, which is a continuation-in-part of Ser. No. 07/490,791,
filed Mar. 8, 1990, now U.S. Pat. No. 5,054,455. All are commonly
assigned.
Claims
What is claimed is:
1. A canister purge system for an internal combustion engine
comprising a canister in which volatile fuel vapors from a fuel
tank are collected and which is periodically purged via a purge
flow path to an intake manifold of an engine under conditions
conducive to canister purging, said purge flow path comprising a
regulator valve through which purge flow from the canister to an
intake manifold is conducted, said regulator valve comprising a
housing having a movable wall that divides said housing into a
first chamber space and a second chamber space, a valve member
disposed in said second chamber space and positioned by said wall
relative to a valve seat in said second chamber space for
controlling the purge flow through said flow path, the positioning
of said movable wall being a function of pressure in said first
chamber space, pressure in said second chamber space, and force
exerted by a spring in a sense biasing said valve member toward
said valve seat, a fixed orifice disposed in said purge flow path
between said second chamber space and the canister for causing
pressure in said second chamber space to at least approximate
manifold vacuum while said valve member is unseated from said valve
seat and the canister is being purged to an intake manifold through
said fixed orifice and regulator valve, said fixed orifice also
establishing an upper limit for the purge flow rate through said
regulator valve to an intake manifold, and an electric vacuum
regulator valve disposed in a control flow path between intake
manifold vacuum and said first chamber space for selectively
delivering a selected percentage of intake manifold vacuum to said
first chamber space.
2. A canister purge system as set forth in claim I further
including a fixed wall that divides said second chamber space into
two second chamber space portions, one of said portions being
bounded by said movable wall and the other of said portions
containing said valve member and said valve seat, said fixed wall
comprising means providing for an operative connection to extend
from said movable wall to said valve member, and said fixed wall
including orifice means to limit the rate at which fluid can flow
between said one and said another portions and thereby damp motion
of said movable wall.
3. A canister purge regulator valve for a canister purge system for
an internal combustion engine wherein volatile fuel vapors from a
fuel tank are collected in a canister that is periodically purged
via a purge flow path, including said purge regulator valve, to an
intake manifold of an engine under conditions conducive to canister
purging, said purge regulator valve comprising a housing having a
movable wall that divides said housing into a first chamber space
and a second chamber space, a valve member disposed in said second
chamber space and positioned by said wall relative to a valve seat
in said second chamber space for controlling the purge flow through
said flow path, the positioning of said movable wall being a
function of pressure in said first chamber space, pressure in said
second chamber space, and force exerted by a spring in a sense
biasing said valve member toward said valve seat, a fixed orifice
disposed in said purge flow path between said second chamber space
and an inlet port of said purge regulator valve that is for
connection to a canister for causing pressure in said second
chamber space to at least approximate manifold vacuum while said
valve member is unseated from said valve seat and the canister is
being purged to an intake manifold through said fixed orifice and
regulator valve, said fixed orifice also establishing an upper
limit for the purge flow rate through said purge regulator valve to
an intake manifold, and an electric vacuum regulator valve having
an inlet adapted to be communicated to intake manifold vacuum and
an outlet communicated to said first chamber space for selectively
delivering a selected percentage of intake manifold vacuum to said
first chamber space.
4. A canister purge regulator valve as set forth in claim 1 further
including a fixed wall that divides said second chamber space into
two second chamber space portions, one of said portions being
bounded by said movable wall and the other of said portions
containing said valve member and said valve seat, said fixed wall
comprising means providing for an operative connection to extend
from said movable wall to said valve member, and said fixed wall
including orifice means to limit the rate at which fluid can flow
between said one and said another portions and thereby damp motion
of said movable wall.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to evaporative emission control systems of
the type that are commonly used in association with internal
combustion engines of automotive vehicles.
In such an evaporative emission control system, excess fuel vapors
from the fuel tank are collected in a canister which must be
periodically purged to the engine's induction system so that the
vapors can pass into o the engine's cylinders for combustion. In
this way, the excess vapors do not escape to atmosphere where they
may otherwise contribute to air pollution. The periodic purging of
the vapor collection canister is conducted when conditions
conducive to purging exist, and therefore it is a customary
practice to have a canister purge solenoid (CPS) valve exercise
control over the venting of the canister to the induction system
and to place the CPS under the control of the engine electronic
control unit (ECU). Because the ECU receives signals representing
various engine operating parameters, it can be programmed to allow
purging of the canister at different rates depending upon the
prevailing engine operating conditions. Thus at certain times,
greater amounts of purging may be permitted while at others, lesser
amounts may be allowed.
Governmental regulations establish limits for the amount of fuel
vapor that is permitted to be emitted from an automotive vehicle to
atmosphere. The establishment of stricter regulations may impose
heavier burdens on evaporative emission control systems such that
the present systems may not be able to achieve compliance.
Accordingly, there is a need for further improvement in the
existing evaporative emission control systems of automotive
vehicles so that increased flow rates of excess fuel vapors can be
successfully handled without sacrificing low flow rate accuracy.
The present invention is directed to a solution for meeting this
need.
Drawing FIGS. 1-4 relate to an embodiment which comprises the
inclusion of a variable orifice in the vapor flow path from the
canister to the induction system and the use of the engine's
throttle to exercise control over the degree of restriction imposed
by the variable orifice on the vapor flow path to the induction
system. The invention of these four drawing figures is the subject
of commonly assigned U.S. Pat. No. 4,995,369 of which Ser. No.
07/490,791, filed Mar. 8, 1990, is a continuation-in-part. The
variable orifice is progressively increasingly restricted as the
engine is progressively increasingly throttled. A purge regulator
that is under the control of the engine ECU also exercises control
over the vapor flow to the induction system. The ECU is programmed
using conventional programming techniques to produce a desired
degree of purge flow regulation in accordance with engine operating
conditions detected by the ECU. Thus, certain principles of the
invention of Ser. No. 07/490,791 contemplate the conjoint control
of the vapor flow from the canister to the induction system by the
throttle's control of the variable orifice and by the ECU's control
of the purge regulator.
A modern internal combustion engine that contains an ECU typically
has a throttle position sensor that provides to the ECU an
indication of the instantaneous throttle position. By having the
variable orifice directly controlled by the throttle, the throttle
position sensor signal is made inherently representative of the
degree of restriction imposed by the variable orifice on vapor flow
from the canister to the induction passage. Thus, the ECU can
"read" the variable orifice and take that reading into account as
it exercises control over the purge regulator. A system embodying
such inventive principles is well suited for providing controlled
canister purging over a large dynamic range extending from engine
idle to wide open throttle. It is also capable of providing a
steadier flow that is beneficial in attenuating hydrocarbon
emission spikes in the engine exhaust.
FIGS. 5 through 9 of the drawings relate to a novel construction
for coupling the purge valve with the movable wall (diaphragm) that
operates it. A rod that is guided for linear motion has one end
connected to the movable wall and the other end to the purge valve.
The connection to the movable wall is through a joint that
essentially precludes the transmission of any bending moment from
the movable wall to the rod. The connection to the valve provides
for a certain wobble of the valve head that is advantageous for
proper seating on the valve seat while preventing fluid leakage
through the connection. The combination of these features enhances
the accuracy of response of the device to commands.
FIG. 10 relates to an embodiment of purge regulator in which the
construction of the vacuum regulator is different from that of the
vacuum regulator of FIG. 5.
FIGS. 11-16 relate to additional embodiments which are in certain
respects improvements upon the embodiments of FIGS. 5-10. A common
feature of the additional new embodiments relates to a tapered
valve element for controlling the purge flow. As the valve begins
to increasingly open from its fully closed condition, the tapered
portion of the valve element coacts with a portion of the flow
passage circumscribed by the valve seat to create a gradual
increase in the controlled restriction that is imposed by the
valve, as distinguished from a more abrupt increase that would
occur in a construction like that of FIG. 5. The advantages of this
result of incorporating a tapered valve element into the purge
regulator include: reduction in the purge flow oscillations which
might otherwise occur in a construction that has a more abrupt
opening characteristic; operating noise reduction due to the
attenuation of the purge flow oscillations; a reduction in the
number of components that are required, thereby enabling meaningful
reductions in overall valve size to be made, and simplifying
fabrication procedures; the ability to attain a more linear
characteristic for flow output vs. signal input; and as a result of
the more linear flow characteristic, better compatability for open
loop operation at low duty cycles (idle purge), yet retaining high
duty cycle compatability for closed-loop operation.
The foregoing features, advantages, and benefits of the invention,
along with additional ones, will be seen in the ensuing description
and claims, which should be considered in conjunction with the
accompanying drawings. The drawings disclose a presently preferred
embodiment of the invention in accordance with the best mode
contemplated at this time in carrying out the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram presenting the preferred embodiment
of regulated flow canister purge system according to the invention
of U.S. Pat. No. 4,995,369.
FIG. 2 is a view looking in the direction of arrows 2--2 in FIG.
1.
FIG. 3 is a view similar to FIG. 2, but illustrating another
position of operation.
FIG. 4 is a graph plot of actual test flow data useful in
explaining certain principles of the invention.
FIG. 5 is a cross section through a preferred embodiment of valve
as disclosed in the two parent applications.
FIG. 6 is an enlarged fragmentary view of a portion of FIG. 5.
FIG. 7 is a transverse cross section taken in the direction of
arrows 7--7 in FIG. 6.
FIG. 8 is an enlarged fragmentary view of a portion of FIG. 6.
FIG. 9 is a plan view of one of the parts of FIG. 8 shown by
itself.
FIG. 10 is a cross section through another embodiment of valve as
disclosed in the most recent parent application.
FIG. 11 is a cross section through a regulated flow CPS valve
containing the tapered valve element improvement referred to
above.
FIG. 12 is a fragmentary enlarged view of the tapered valve element
of the regulated flow CPS valve of FIG. 11.
FIG. 13 is a view in the direction of arrows 13--13 in FIG. 12.
FIG. 14 is a cross section through another embodiment of regulated
flow CPS valve containing the tapered valve element
improvement.
FIG. 15 is a cross section through a further embodiment of
regulated flow CPS valve containing the tapered valve element
improvement.
FIG. 16 is a fragmentary enlarged view of the tapered valve element
of the regulated flow CPS valve of FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An automotive vehicle that is powered by an internal combustion
engine includes a fuel tank 10 and a throttle assembly 12. Excess
fuel vapors that are vented from tank 10 are collected in a
canister 14. The collected vapors are exhausted from canister 14 to
the air induction passage 16 that passes through the body 18 of
throttle assembly 12 with the passage of the vapors being under the
conjoint control of a variable orifice valve 20 and a purge
regulator 22.
Variable orifice valve 20 is operated directly by the throttle
mechanism 24 of throttle assembly 12. Valve 20 comprises a body 26
that is fixedly mounted on the outside wall of throttle body
18.
Throttle mechanism 24 comprises a shaft 28 that is arranged
perpendicular to the direction of induction air flow through
passage 16 and is journaled for rotation on the throttle body.
Shaft 28 is operated by a crank 30 that is linked to the vehicle
accelerator pedal (not shown). A throttle blade, or butterfly, 32
is fastened to shaft 28 within passage 16. The extent to which
shaft 28 is operated by crank 30 determines the position of
butterfly 32 within passage 16 and hence the degree of throttling
of the engine.
The end of shaft 28 opposite crank 30 passes through body 26 to
operate a throttle position sensor (TPS) 34 that is disposed
outboard of variable orifice valve 20. TPS 34 is one of a number of
inputs to an engine electronic control unit (ECU) 36, the other
inputs to the ECU not appearing in FIG. 1. TPS 34 provides to ECU
36 an electrical signal indicative of the instantaneous throttle
position.
ECU 36 controls a number of engine operating functions, such as
fuel, spark, etc. It also exercises control over purge regulator
22.
Details of variable orifice valve 20 include an inlet nipple 38
providing for the connection of a hose 40 from canister 14 and an
outlet nipple 42 providing for connection of a hose 44 to purge
regulator 22. Disposed within the interior of valve body 26 and
affixed to shaft 28 is a valving member in the form of a rotary cam
46.
As shown in FIGS. 2 and 3, cam 46 has a profile 48 that is adapted
to coact with the interior end of nipple 42 as the throttle shaft
rotates thereby providing a variable restriction. FIG. 1 shows
throttle blade 32 in essentially the wide open throttle position,
and the corresponding position portrayed by FIG. 2 represents the
minimum restriction position of the variable orifice valve.
As the throttle is progressively operated from the wide open
throttle position toward engine idle position, cam 46 rotates in
the clockwise sense as viewed in FIG. 2 to progressively
increasingly restrict the variable orifice. At engine idle, as
represented by FIG. 3, the variable orifice imposes maximum
restriction to flow from canister 14. Since TPS 34 is being
concurrently operated with cam 46, the TPS signal to ECU 36 is
inherently representative of the degree of restriction being
imposed by the variable orifice valve on vapor flow from the
canister. In this way, the ECU can "read" the TPS to determine the
restriction being imposed on the flow from the canister.
Purge regulator 22 may be considered to comprise two conventional
components, namely an electronic vacuum regulator (EVR) 50 and a
vacuum regulator 52. A device like that described in commonly
assigned U.S. Pat. No. 4,850,384 is suitable for EVR 50. The EVR
has a vacuum inlet nipple 54, an atmospheric vent 56, and a vacuum
outlet nipple 58. Nipple 54 is connected to a vacuum signal source,
namely engine manifold vacuum 60, by a hose 62. The EVR contains a
solenoid that is pulse width modulated by ECU 36. In this way the
vacuum level that appears at nipple 58 is controlled by ECU 36.
Vacuum regulator 52 comprises a control nipple 64 that is connected
to nipple 58 by a hose 66. It also has an inlet nipple 68 to which
hose 44 is connected and an outlet nipple 70 connected by a hose 72
to a nipple 74 that extends through the wall of throttle body 18 at
a location downstream of throttle blade 32. Vacuum regulator 52 is
responsive to the vacuum output of EVR 50 to regulate the flow
through the vacuum regulator from nipple 68 to nipple 70. The
larger the vacuum delivered to nipple 64, the more flow is
permitted from nipple 68 to nipple 70, and the smaller the vacuum
delivered to nipple 64, the less flow is s permitted from nipple 68
to nipple 70. And so it can be appreciated that the vapor flow that
is permitted by purge regulator 22 is under the control of ECU
36.
Accordingly, it can be further appreciated that the vapor flow from
canister 14 to induction passage 16 is a function both of the
throttle position as the throttle shaft controls variable orifice
valve 20, and of the degree to which ECU 36 permits flow through
purge regulator 22.
The effect of variable orifice valve 20 on the canister purge
process can be nicely explained with reference to FIG. 4. For a
given pressure drop across the valve, there exists a corresponding
graph plot that charts the flow rate through the valve as a
function of throttle blade position. FIG. 4 presents, by way of
example, a series of six individual graph plots, each of which
corresponds to a specific pressure drop across the variable orifice
valve 20. The pressure drops that are represented in FIG. 4 are, in
terms of inches of mercury (Hg), 0.5 inch, 1.0 inch, 1.5 inches,
2.0 inches, 3.0 inches, 4.0 inches. For a given pressure drop, the
corresponding graph plot depicts the flow rate through the variable
orifice valve 20 as a function of the amount of throttle blade
opening between fully open and closed throttle conditions. Stated
another way, for a given throttle position, the flow vs. pressure
drop characteristic is defined for valve 20. Because the throttle
position sensor provides the ECU with the capability of reading the
variable orifice, suitable mapping of the ECU such as in the
exemplary manner of FIG. 4 enables the ECU to know the
corresponding flow vs. pressure drop characteristic of variable
orifice valve 20 for specific throttle blade positions. The ECU can
then take this into account when setting purge regulator 22.
The provision of the variable orifice valve 20 under the control of
the throttle endows the emission control system with a wide dynamic
range, allowing good control from engine idle to wide open
throttle. As a result, the system can achieve compliance with
stricter evaporative emission standards. The solenoid of EVR 50 is
operated by a frequency of signal from the ECU which is
considerably higher than that used to control previously used CPS
valves. (125-150 hz vs 10-20 hz, typically). This serves to
attenuate hydrocarbon spikes in exhaust emission.
FIGS. 5-9 present details of a purge regulator 80. It comprises an
EVR 82 and a vacuum regulator 84. Although the illustrated purge
regulator embodies the EVR and the vacuum regulator in a single
unit, they could be embodied as two separate devices with a
suitable connection from the EVR to the vacuum regulator.
EVR 82 is essentially conventional, comprising a vacuum inlet 86 to
which vacuum is supplied and an outlet 88 at which a percentage of
the vacuum is delivered, as determined by an electrical control
signal supplied to an electrical input 90. The vacuum from outlet
88 is supplied as an input to vacuum regulator 84.
Vacuum regulator 84 may be considered to comprise an actuator
portion 92 and a valve portion 94. Actuator portion 92 comprises a
movable interior wall 95 that divides two variable volume chamber
spaces 96 and 98 whose respective volumes establish the position of
movable wall 95. Regulated vacuum from outlet 88 is supplied to
chamber space 96. Chamber space 98 is in communication with the
fuel vapor storage canister via valve portion 94.
Valve portion 94 comprises an inlet nipple 100 via which it is
placed in communication with the fuel vapor storage canister, and
an outlet nipple 102 via which it is placed in communication with
the engine intake manifold. A valve 104 that is operated by
actuator portion 92 controls communication through valve portion 94
between inlet nipple 100 and outlet nipple 102. FIGS. 5 and 8 show
valve 104 in seated position on a valve seat 106 preventing flow
from nipple 100 to nipple 102.
Valve 104 is coupled to movable wall 95 by means that includes a
straight circular cylindrical rod 108. Rod 108 is guided for
straight-line motion toward and away from valve seat 106 by means
of an annular guide member 110 which is secured to the housing 112
by any suitable means such as 114. Guide member 110 comprises a
cylindrical sleeve 116 which is co-axial with both movable wall 94
and valve seat 106 and through which the central portion of rod 108
passes. Guide member 110 also comprises a hole 118 which serves to
communicate chamber space 98 with whatever pressure or vacuum may
occur on the canister side of valve 104. Hole 118 is an orifice
which is sized to control the rate at which flow can pass between
chamber space 98 and the space 109 within which valve 104 is
disposed. The net result is the imposition of a damping force on
movable wall 95 which serves to prevent valve fluttering that might
otherwise occur in response to rapidly occurring changes in
pressure differential across the orifice (i.e. between chamber
space 98 and space 109). The orifice effect may also have a
tendency toward linearizing the response of the vacuum
regulator.
It is also to be observed that FIG. 5 shows the presence of a fixed
orifice 111 in the wall between nipple 100 and space 109. Orifice
111 is effective to ensure that the magnitude of vacuum in space
109 at least approximates the engine manifold vacuum, while also
establishing an upper limit for the flow rate through the vacuum
regulator. Orifice 111 may be present either with or without a
co-operative association of purge regulator 80 with a variable
orifice valve, like valve 20 of FIGS. 1-4. Any given configuration
of a regulated flow canister purge system will of course be
designed for compliance with a defined engineering specification,
and hence one configuration may comprise a variable orifice valve,
another, a variable orifice valve connected to a purge regulator
(with or without fixed orifice), another only a purge regulator
with an orifice.
A purge regulator can be designed to service different o
requirements without major modification. Rather than making the
purge regulator of FIG. 5 to have an integral fixed orifice, the
purge regulator can be constructed to have the opening between
space 109 and nipple 100 equal to the cross-sectional area of
nipples 100,102, and adopting the nipple to receive an inserted
orifice disc. Such an orifice disc will close most of the nipple
except for an orifice in the disc. The area of the orifice in any
given orifice disc may be selected as required for the particular
system into which the purge regulator is to be installed.
The end of rod 108 that is opposite the end containing valve 104 is
coupled with movable wall 95 by means of a joint 120 that is
designed so as to be incapable of transmitting any significant
bending moment from movable wall 95, through the rod, to the valve.
This attribute is important because the action of movable wall 95
on the rod might otherwise impart a bending moment which could
adversely affect rod displacement and hence impair the accuracy of
the rod's positioning of valve 104. A principal cause of the
tendency of movable wall 95 to impart a bending moment to rod 108
is due to the fact that the wall is resiliently biased by a helical
coil spring 122 in a sense that urges valve 104 toward seating on
seat 106, and the force distribution acting on the movable wall is
not circumferentially uniform. Hence, the movable wall has a
tendency to tilt, or cock about its axis, but adverse consequences
of this tendency are avoided because of the provision of joint
120.
Joint 120 comprises a spherically contoured surface 124 in o
movable wall 95 acting through an element 126 on the end of rod
108. Element 126 comprises a head 128 having on one side a fiat
surface 130 against which surface 124 is in tangential contact. A
cylindrical annular shank 132 extends from the opposite side of
head 128 and is united to the rod end by an interference-fit
therewith. The distal end of shank 132 is rounded at 134 for
seating in a complementary rounded depression 136 in an annular
member 138. The outer margin of member 138 is shaped to form a seat
for one end of a further helical coil spring 140 that is disposed
between member 138 and member 110, the latter having a spring seat
for the opposite end of the spring. Spring 140 functions to keep
the surface 130 of head 128 against surface 124 (i.e., capture
element 126 between wall 95 and member 138) as the movable wall is
positioned within the housing 112. The rounded fitting of member
138 to the distal end of shank 132 prevents spring 140 from
transmitting any significant bending moment to the joint.
FIGS. 5, 8, and 9 present details of valve 104 and its attachment
to rod 108. Valve 104 comprises an elastomeric part 142 and a
relatively more rigid metal part 144. Part 144 is a circular metal
disc that is disposed interiorly of an annular head 146 of
elastomeric part 142. Part 144 has an aperture 148 of the shape
illustrated in FIG. 9 that provides for attachment of the part to
rod 108 in such a manner that it can wobble to a certain extent on
the rod. Part 142 further comprises an annular sleeve 150 extending
from head 146 and seals the valve to the rod. The rod end is shown
to have axially spaced circular serrations 152 that aid in the
sealing and retention of the head on the rod end. Head 146 also
contains a circular ridge 154 for sealing contact with valve seat
106. The design of valve 104 is beneficial in attaining proper
sealing, especially in mass production usage, because the head can
self-adjust to the seat while sealing of the valve to the rod end
is assured.
The device operates in the following manner. Movable wall 95 is
axially positioned in accordance with the pressure differential
between the two chamber spaces 96, 98. Since a controlled
percentage of manifold vacuum is applied to chamber space 96, the
relative volumes of the two chamber spaces and hence the position
of wall 95 are related to the percentage manifold vacuum applied to
the vacuum regulator from the EVR. This will produce a
corresponding positioning of valve 104 to control the flow of vapor
from the canister to the manifold. In this way the purging of the
canister is regulated to occur during conditions of engine
operation s that are conducive to purging.
FIG. 10 shows a purge regulator 160 comprising an EVR 162 and a
vacuum regulator 164. EVR 162 is essentially like EVR 82,
comprising a vacuum inlet 166 for connection to manifold vacuum and
an outlet 168 that is communicated to a chamber space 170 of vacuum
regulator 164 corresponding to the chamber space 96 of vacuum
regulator 84. The vacuum that is delivered to chamber space 170
from EVR 162 is a percentage of the vacuum input at inlet 166 as
determined by an electrical control signal supplied to the EVR's
solenoid 172.
Vacuum regulator 164 comprises a housing 174 that is divided into
two chamber spaces 170, 176 by a movable wall 178. Housing 174 has
an inlet nipple 180 and an outlet nipple 182. The inlet nipple is
open to chamber space 176. A valve seat 184 is fashioned within
chamber space 176 around outlet nipple 182.
Wall 178 comprises an outer annular part 186, and a rigid central
part 188. The face of part 188 which is toward seat 184 contains a
valve member in the general form of a circular disc 190. A helical
coil spring 192 which is disposed in chamber space 170 bears
against part 188 to resiliently urge disc 190 into seating on seat
184 so that chamber space 176 is closed to outlet nipple 182.
Although not shown in FIG. 10, it should be understood that there
is a suitable orifice between chamber space 176 and the canister so
that the vacuum in chamber space 176 at least approximates manifold
vacuum.
Purge regulator 160 operates as follows. A percentage of manifold
vacuum is delivered to chamber space 170. When the vacuum in that
chamber space rises to a certain magnitude, the bias of spring 192
is overcome, and disc 190 unseats from seat 184 to allow flow from
the canister through the vacuum regulator to the manifold.
Concurrently, the vacuum magnitude in chamber space 176 begins to
rise. In a steady state condition, there will be a regulated
balance between the two chamber spaces that creates a certain size
orifice between disc 190 and seat 184, and hence a corresponding
flow rate between the canister and manifold. If the manifold vacuum
changes and the control signal from the ECU remains constant, then
the resulting change in force caused by the change in vacuum within
chamber space 176 will act upon moveable wall 178 causing the
relationship between disc 190 and seat 184 to adjust until o there
is a regulated balance between chambers 170 and 176. The newly
established relationship between the disc and seat will adjust the
flow from the canister to the intake manifold so that it is
essentially the same flow prior to the increase in manifold vacuum.
In this manner the purge regulator maintains a constant flow from
the canister to the intake manifold when the intake manifold vacuum
changes.
For example, when the intake manifold vacuum increases there would
normally be an associated increase of flow between the canister and
intake manifold. However, the increased force caused by the vacuum
will act upon moveable wall 178 and disc 190 causing them to move
in an axial direction towards seat 184. As the spacing between the
disc and seat is reduced it will impose an increased restriction to
flow through regulator 164. The restriction to flow will continue
to increase until it causes the vacuum (and resulting force) within
chamber 176 to drop to a level that will provide a regulated
balance with the vacuum and the bias spring (and resulting force)
in chamber 170. When this regulating condition is achieved the
relationship between the disc and seat within regulator 164 will
provide a flow between the canister and intake manifold that is
relatively unchanged from the level of flow prior to the change of
intake manifold vacuum.
If on the other hand, the manifold vacuum remains constant and the
control signal from the ECU changes, then the electronic vacuum
regulator will change the level of vacuum within chamber space 170.
The o resulting change in force will act in conjunction with the
force of bias spring 192 on moveable wall 178 causing the
relationship between disc 190 and seat 184 to adjust until there is
a new regulated balance between chambers 170 and 176. The newly
established relationship between the disc and seat will provide a
change in flow from the canister to the intake manifold that is
relative to the percentage change in the control signal from the
ECU. In this manner an electrical signal can provide control over
the flow through the purge regulator.
For example, when the percentage of electrical control signal to
the purge regulator is decreased the EVR reduces the level of
vacuum in chamber space 170. The reduction of vacuum and hence
force acting on moveable wall 178 will allow the force of bias
spring 192 working in conjunction with the resulting force of the
vacuum in chamber 176 to move disc 190 and moveable wall 178 in an
axial direction towards seat 184. As the spacing between the disc
and seat is reduced it will impose an increased restriction to flow
through regulator 164. The restriction to flow will continue to
increase until it causes the vacuum (and resulting force) within
chamber 176 to drop to a level that will provide a regulated
balance with the vacuum and the bias spring (and resulting force)
in chamber 170. When this regulating condition is achieved the
relationship between the disc and seat within regulator 164 will
provide a lower regulated flow between the canister and intake
manifold that is relative to the control signal applied to the
purge regulator.
Accordingly, purge regulator 160 performs in like manner to purge
regulator 80, but it may possess a somewhat larger tolerance on
regulation. Such increased tolerance may be acceptable in certain
canister purge systems, and hence purge regulator 160 offers a less
costly alternative to purge regulator 80 for such uses.
FIGS. 11-13 relate to a purge regulator 80A which is essentially
like purge regulator 80 with the exception of the valve element. In
purge regulator 80A, the valve element is 104A, whereas in purge
regulator 80, it is 104. Like parts of the two embodiments are
designated by like reference numerals.
Valve element 104A comprises two elements that are assembled
together, namely a body 200 and a seal 202. Body 200 comprises
axially successive portions which are a socket portion 204 that
provides for attachment of the valve element to the lower barbed
end of rod 108, a circular flange portion 206 that provides for the
attachment of seal 202 to body 200, and a tapered portion 208 that,
when the valve is open to conduct purge flow from nipple 100 to
nipple 102, coacts with an adjacent straight circular cylindrical
portion 207 of the purge flow passage that is o circumscribed by
valve Seat 106 to set the restriction that the purge regulator
imposes on the purge flow.
Body 200 may be fabricated from any suitable material, such as fuel
resistant plastic, which retains shape, yet enables socket portion
204 to be pushed onto the end of rod 108 for assembly. Seal 202 is
made from any suitable material, a fluorosilicone for example, that
will fit to body 202 in a sealed manner, and that will also seal to
seat 106 when the valve is closed. Seal 202 has a general circular
annular shape that sealedly adheres to the axial face of flange 206
that faces seat 106. The seal may be insert-molded onto body 200,
and the drawing Fig. illustrates the use of several plugs 210 that
extend from the seal, pass through holes or slots in the flange,
and terminate in heads at the opposite face of the flange, .to
provide a mechanical interference so that the assembly of the seal
to the body does not have to rely exclusively on adhesion of the
seal material to the body material.
FIG. 12 shows the closed condition with seal 202 sealed against
seat 106. As soon as actuator portion 92 has elevated valve element
104A sufficiently to separate seal 202 from seat 106, the valve
opens. Depending upon the specific size and shape of tapered
portion 208 relative to passage portion 207, a point will be
reached, early in the valve opening, where the restriction imposed
by the the valve on the purge flow will be determined by the
coaction between tapered portion 208 and passage portion 207. In
general, this point will occur very early in the valve opening.
The tapered valve element results in a more gradual opening, as
distinguished from the more abrupt opening that characterizes the
regulator of FIG. 5. This provides better control and reduces
sudden s vacuum pulsations. The embodiment of FIG. 5 includes a
dampening orifice 118, and although FIG. 11 still shows the
presence of such an orifice, the use of a tapered valve element in
the manner of FIG. 11 will make it possible in many instances, such
as the examples of FIGS. 14 and 15 to be hereinafter described in
detail, to eliminate the deliberate dampening effect that was
included in the FIG. 5 embodiment.
The tapered portion 208 that is illustrated in FIGS. 11-13
comprises in toto a non-linear taper that is composed of two
piecewise linear frusto-conical sections 208A and 208B
respectively. Section 208A begins at seal 202 and ends at section
208B. Section 208B has a steeper slope than section 208A so that
once section 208A has moved out of passage section 207, the
restriction imposed by the regulator on the purge flow diminishes
at a faster rate. By designing the tapered portion in this way, the
regulator will have a dual-slope function, meaning a different
slope depending on which particular section 208A or 208B is
coacting with the passageway portion at any given point in time.
Other profiles for the taper are of course possible.
FIG. 14 presents another regulator 260 which includes an EVR 162
exactly like the EVR of FIG. 10. Like numbers designate like parts.
Regulator 260 comprises a housing 274 that is divided into two
chamber spaces 270, 276 by a movable wall 278. Housing 274 has an
inlet nipple 280 and an outlet nipple 282. The inlet nipple is open
to chamber space 276. A valve seat 284 is fashioned within chamber
space 276 around outlet nipple 282.
Wall 278 comprises an outer annular part 286 and a rigid central
part 288, that latter having a spring seat 290 for one end of a
helical coil spring 292 which is disposed in chamber space 270 and
whose opposite end bears against a spring seat 294 affixed to the
common wall between housing 274 and EVR 162 such that a tapered
valve element 296 centrally disposed on wall 278 within chamber
space 276 is resiliently biased into seating closure against valve
seat 284. There is a suitable orifice 298 between chamber space 276
and the canister so that the vacuum in chamber space 276 at least
approximates manifold vacuum.
Valve element 296 is like the preceding tapered valve element in
that it has a circular annular portion 300 that seals against seat
284 when the valve is closed and a tapered portion 302 that, when
the valve opens, coacts with the adjacent straight circular
cylindrical flow passage portion circumscribed by the valve seat to
set the valve's restriction to purge flow. It differs in that the
tapered portion 302 has a single, rather than a dual-slope taper.
It is to be noticed that this embodiment is of both reduced size
and number of parts from the embodiment of FIG. 11.
FIGS. 15 and 16 disclose an embodiment of regulator 380 which
includes an EVR 82 exactly like the EVR of FIG. 11, but has a less
complicated actuator and valve portion 392. Like numbers designate
like parts. This latter portion comprises a housing 394 that is
divided into two chamber spaces 396, 398 by a movable wall 400.
Housing 394 has an inlet nipple 402 and an outlet nipple 404. The
inlet nipple is open to chamber space 398. A valve seat 406 is
fashioned within chamber space 398 around the entrance leading to
outlet nipple 404.
Wall 400 comprises an outer annular part 407 and a rigid central
part 408, that latter having a spring seat 410 for one end of a
helical coil spring 412 which is disposed in chamber space 396 and
whose opposite end bears against a spring seat 414 affixed to the
common wall between housing 394 and EVR 82 such that a tapered
valve element 416 within chamber space 398 is resiliently biased
into seating closure against valve seat 406. There is a suitable
orifice (not appearing in the Fig.) between chamber space 398 and
the canister so that the vacuum in chamber space 398 at least
approximates manifold vacuum.
Valve element 416 is like the preceding tapered valve elements in
that it has a circular annular portion 418 that seals against seat
406 when the valve is closed and a tapered portion 420 that, when
the valve opens, coacts with the adjacent straight circular
cylindrical flow passage portion circumscribed by the valve seat to
set the valve's restriction to purge flow. It is also like the
embodiment of FIG. 14 in that the tapered portion 420 has a single,
rather than a dual-slope taper. It differs in that it is not
attached to movable wall 400, but rather is resiliently biased
against the central domed region of part 408 by means of a small
helical spring 422 so that it follows the motion of the central
region of the movable wall. This is the o same type of joint that
was used between the movable wall and the rod 108 in FIGS. 5 and 11
to avoid the transmission of bending moment from the movable wall
to the valve element.
The bottom wall of housing 394 comprises a socket within which
spring 422 is disposed. The lower end of the spring bears against
the bottom wall of the socket while the upper end of the spring
bears against several circumferentially spaced apart protrusions
424 near the lower end of tapered portion 420. The force exerted by
spring 422 on the valve element is comparatively small so as not to
adversely interact with spring 412 and is just sufficient to keep
the valve element in contact with the movable wall so that the
valve element will follow motion of the movable wall. The valve
element is constructed to have a body 426 that includes a circular
flange 428 at the top, and a circular annular seal 430 that is
insert molded onto the body. It is to be noticed that this
embodiment is of both reduced size and number of parts from the
embodiment of FIG. 11. Because this embodiment, unlike the
embodiments of FIGS. 11 and 14, lacks a direct attachment of the
valve element to the movable wall, any question of alignment of the
valve element with the movable wall that could adversely affect the
positioning of the valve element by the movable wall is rendered
moot, and as a result hysteresis in reduced.
The embodiments of FIGS. 11-16 function in like manner to the
embodiments of FIGS. 5-10, with the enhancement provided by the
tapered valve element.
The invention can therefore be seen to constitute an improvement in
evaporative emission control systems. While a presently preferred
embodiment of the invention has been illustrated and described, it
will be appreciated that principles are applicable to other
equivalent embodiments within the scope of the following
claims.
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